Disposable pilot valve



Aug. zo, 1957 E. F. DYSQN 2,803,258

DISPOSABLE PILOT. VALVE Filed June 16, 1954 2 Sheets-Sheet l 25' nu j?,

Aug. 20, 1957 E. F. DYSON 2,803,258

DISPOSABLE PILOT VALVE 2 Sheets-Sheet 2 Filed June 16, 1954lill/lllIl'lllllllllllllnlllI/llln V/lll//l//A United States PatentDISPOSABLE PILOT VALVE Ernest F. Dyson, Meriden, Conn., assignor to TheBristol Company, Waterbury, Conn., a corporation of ConnectcutApplication June 16, 1954, Serial No. 437 ,266 13 Ciaims. (ci. 137-82)This invention relates to pilot valves for Huid-actuated controlapparatus, and more especially to a removable and disposable pilot valvefor pneumatic control devices. This application is a continuation-impartof my application for Relay Valve, filed December 1'1, 1952, SerialNumber 325,469, now Pat. No. 2,780,242.

A common form of pilot valve for pneumatic control involves a seatingmember subject to actuation by Variations in fluid pressure on adiaphragm or in a capsular spring, the seating member cooperatingwith aseat to provide a variable closure in a conduit conducting compressedair to a pneumatic motor-operated control apparatus. Said huid pressureis regulated by means of a supply-and-waste member wherein the admissionof air is limited by means of a fixed restriction in the supply and theescape is controlled by means of a vane, baille, apper or obturator moreor less juxtaposed to a small escape orifice communicating with theatmosphere. The principle of these pilot valves is well known, and theyare available in a considerable variety of forms. In general, however,they are delicate in construction, and of such cost that in the event ofdamage or malfunctioning they may not economically be discarded butrequire to `be repaired and readjusted, with consequent uncertain andhigh costs as well as indefinite shut-downs of associated plantequipment. v

It is an obiect of the present invention to provide a pilot valve havingdesirable operating characteristics and adapted to manufacture on aproductionbasis by automatic machinery, and hence of such low cost as tobe economically disposable in case of damage. Y

It is a further object to provide a valveof the above type which mayquickly be removed and replaced without the need for special tools orgreat skill in manipulation.

It is a further object to provide a pilot valve having incorporated inits structure the constriction essential to the supply-and-waste methodof control, said constriction being of a nature not subject to cloggingor stoppage by foreign particles entrained in theair stream.

In carrying out the purposes of the invention there may be provided apilot valve assembly whose metal parts are principally stamped or spunfrom sheet material, or cut from standard tubing, and whose non-metalliccomponents are comprised in simple diaphragm elements of uniformthickness and a plug member either moulded from suitable thermosettingmaterial or machined from a plastic bar stock. The design embodying theprinciples of the invention eliminates the need for crossdrilling ortapping, or the shaping and fitting of tubular conduits, and requires nobolts, screws or rivets in its assembly. q

Other features and advantages of the invention will be hereinafterdescribed and claimed.

in the drawings:

Figures l and 2 are side elevations in section, showing in its twoextreme operating positions a pilot valve embodying the principles ofthe invention.

ICC

Figure 3 is an isometric exploded view of the valve, showing most of itscomponent parts.

Figure 4 is a detail of an element of the assembly shown in Figures land 2.

Figure 5 is a sectional View showing an alternative form of a componentof the valve structure.

While the apparatus of the present invention and the immediatelyassociated instrumentalities are adapted to operation by any suitableexpansible tiuid, the most cornmon medium for this purpose is compressedair at a supply pressure of the order of 20 pounds per square inch; andin the interest of simplicity and clarity the description will be givenas applicable to such a system, without in any way excluding the use ofother uid agents should their utilization be found expedient.

Referring now to the drawings:

The numeral 1t) designates a portion of a controller component commonlyknown as an air-block, formed usually of metal, and having therein oneor more openings, each providing a receptacle for one of the pilotvalves to which the present invention is directed. Each of the openingsin the air-block 10 comprises an inner cavity 12 and an outercounterbored portion 13 separated from said cavity by a section l5havingV formed therein a female knuckle thread. The inner cavity 12communicates with an air supply source 16, and the outer portion 13 witha conduit 17 providing communication to the diaphragm motor orcorresponding actuating element of a control valve 18 lto be operatedthrough the functioning of the pilot valve to which the invention isdirected. The outer edge of the counterbored portion 13 where theopening intersects the surface of the airblock llil is machined to asmooth surface, either forming a right angle, or slightly chamfered forsealing engagement With a further element now to be described.

The principal supporting and enclosing body of the pilot valve formingythe present invention comprises a shell member 2i) (Figure 3),preferably formed from a single piece of sheet metal stock, and having acircular flanged upper portion 21, a cylindrical intermediate portion22, a conically conformed or lfunnel section 23, a threaded lowerportion 24, and a plane inwardly-extending annular portion 25. Theflanged portion 21 is substantially saucer-shaped and is provided with aradiallyextending edge part 26 adapted for engagement by a furthermember presently to be described. The at base of the portion 21 ispierced with a plurality of openings 27, one function of which is toprovide unobstructed communication between the interior and the exteriorof that portion of the assembly.

The cylindrical portion 22, extending as a broad stem downwardly fromthe base of the saucer portion 21, is formed to an external diametersomewhat greater than that of the machined edge of the counterboredopening 15.3, and provides internal space to contain certain mechanicalelements hereinafter to be set forth. The conical section 23 is taperedfrom a maximum outside diarneter corresponding to that of thecylindrical portion 22 to a minimum diameter less than that of thecounterbore 13, thus providing for sealing engagement between the outersurface of said conical portion and said machined edge, as on a line23', when forced into intimate contact therewith.

The portion 24 is formed with a male knuckle thread to cooperate withthe thread 15 in the block 10, whereby junction between the sections z3and 24, and within the circular line'23', the shell member 20 isprovided with one or more perforations 28 permitting free communicationbetween the interior of the shell and the counterbore 13.

In order to complete the closure of the shell member Y there is provideda circular domed or dished top member 30 conformed to engage the flangedportion 21 and having an axially extending cylindrical edge portion 31adapted to encircle the radially projecting edge 26 of said flangedportion and to be secured thereto as presently to be described. Themember 30 is further provided with a centrally located upwardlyextending boss portion having therein a small aperture 32 adapted to thepassage of air therethrough.

Centrally located within the flanged portion 21 and having a diameterofthe order of of the same is a circular plate 33 to the center of whichis integrally secured, as by welding, brazing or soldering, a straighttubular member 34 having a capillary bore. Said tubular lmember projectsperpendicularly through said plate extending upward .an appreciabledistance from the top surface thereof, and downward to the interior ofthe cavity 12; and, with said plate, the tubular member 34 is free forlimited axial displacement. Juxtaposed to the plate 33 and flatlyengaging its upper surface is a flexible circular diaphragm 35 formed ofsheet rubber, neoprene, or equivalent resilient material, and ofsufficient diameter to lie within the edge part 31 of said top member 30for clamping engagement thereby against the outwardly extending edge 26of the flanged portion 21. The upwardly extending projection of thetubular member 34 passes tightly through a central perforation in thediaphragm 35.

Positioned within the opening of the annular flat portion 25 of theshell 20, and free for limited axial displacement therein, is a plugmember 36 formed of slightly resilient material such as hard rubber ormoulded or machined plastic having a central bore to make a sliding fitwith the exterior surface of tubular member 34 and having a cylindricalportion extending upwardly within the threaded and the conical portionsof the shell 20 and an enlarged portion extending below the flat shellportion 25 and adapted to lie within the cavity 12 when the valveassembly is fitted into the airblock 10. Between said extended portionsof the plug member 36 is a conical portion 37 conformed to engage theinner edge of the circular opening in the portion 25 when said plug isforced in an upward sense, and thereby to establish a fluid-tight sealtherewith. The inner end of the upwardly extending portion of the plugmember 36 is porvided with a groove 38 adapted to receive a retainingring 39; and against the lower side of said ring bears the upperextremity of a conically conformed compression spring 40, whose lowerextremity rests upon the inner face of the annular shell portion 25, andis centrally constrained therein by the threaded portion 24. The uppersurface of the plug member 36 is finished smooth to provide a surfacefor sealing with a member now to be described.

Coaxially surrounding the portion of the tubular member 34 between theplug member 36 and the plate 33 is an extended annular sleeve or collar41 having an internal diameter substantially greater than the outside ofsaid tubular member, and having its lower end faced to engage the uppersurface of the plug member 36, and when so engaged to form asubstantially fluid-tight seal. The upper end of the sleeve 41 isadapted to bear against the lowersurface of the plate 33, and is eithercastellated or perforated in order that, while providing-firm mechanicalengagement therewith, it cannot interfere withV free fluid communicationbetween the interior of said sleeve and the space below said plate. Fora portion of its axial length toward its upper end the cylindricalouter'surface of the sleeve 41 is reduced in diameter, and fittedto'this part is a circular plate member 43 of'somewhat smaller diameterthan the interior of the cylindrical portion22 of the shell 21, andpreferably having a downwardly turned edge portion. Upon the platemember 43 rests a flexible diaphragm 44 of greater diameter than saidshell portion 22 and adapted to engage the interior of the flat base ofthe flanged shell portion 21. A circular plate 45, preferably ofslightly less diameter than the plate 43, rests upon the upper surfaceof the diaphragm 44; and the upper extremity of the sleeve 41 is flaredoutwardly to engage said plate 45, whereby to clamp the diaphragm 44between the plates 45 and 43, and to secure the same into an assemblyintegral with said sleeve. An annular plate 46 having an internaldiameter substantially the same as that of the shell section 22, andprovided with perpendicularly projecting lugs 47 is adapted to lie uponthe outer edge of the diaphragm 44, with the lugs extending through theopenings 27, whereby the latter may be crimped beneath the lower face ofthe flanged portion 21 for clamping and sealing the diaphragm 44 to saidflanged portion and isolating the interior of the lower part of theshell member from the surrounding atmosphere. It will be understoodthat, since the lugs 47 do not completely fill the openings 27, theyprovide substantially no obstruction to the free movement of airtherethrough. A conical compression spring 48 is extended between theinterior surface of the conical portion 23 and the lower face of theplate 45, whereby to urge the assembly, including the sleeve 41, intoengagement with the lower surface of plate 33.

In` assembling the above-described component parts into a complete pilotvalve unit, the plug member 36 is first passed into the lower part ofthe shell 20 until its tapered portion 37 engages the interior of thecircular opening in the annular bottom portion 25 of said shell. Thespring 40 is then placed within the threaded portion of said shell withits larger diameter toward the bottom and its smaller diameterencircling the upper part of the plug member 36. The spring is thencompressed and the retaining ring 39 fitted within the groove 38,whereby the plug 36 will tend to be-held in sealing engagement with theannular shell portion 25. The spring 48 is then placed within theportion 22 of the shell 20 with its larger diameter resting in thetapered portion 23. The component comprising the sleeve 41 and theplates 43 and 45 with the diaphragm 44 clamped therebetween is thenpositioned with the bottom portion of said sleeve resting upon the topsurface of the plug member 36. The plate 46 is placed upon the diaphragm44 with its lugs 47 passing around the edge of the same and projectingdownward through the several openings 27 in the member 20. Said lugs arethen forcibly bent inward, clamping the lower part of the assembly intoa unit and forming within the lower part of the shell 20 a chamber 49separated from the upper part by the flexible diaphragm 44, and from thecavity 12 by the plug member 36.

The component comprising the plate 33 and centrally attached capillarytube 34 is then positioned upon the flared edge of the sleeve 41 withsaid tube passing through the bore of the plug member 36. The diaphragm35 is placed upon the top of the plate 33 with the upper extremity ofthe tube 34 projecting through the central opening therein; and the topmember 3f) placed over the same with its cylindrical edge portion 31encircling the periphery of the diaphragm 35 and the flanged edge 26 ofthe shell 2f). The edge 31 is then rolled or spun about the encircledparts, completing the assembly of the unit, and separating the upperpart thereof into two compartments, an upper chamber 50, communicatingwith the atmosphere through the orifice 32 and with the cavity 12through the capillary bore of the tube 34, and a lower chamber 51communicating with the interior of the sleeve 41 through the opening inthe flared end thereof, and also in free communication with theatmosphere through theopenings 27 in the shell 20. Thus, the interior ofthe sleeve 41 is at all times at substantially atmospheric pressure.

v -sehe'r'einbefore 'pointed out, when the pilot valve a's-A sembly isscrewed into the block by means of the mating threaded surfaces withwhich said parts are provided, the lower portion of said thread servesas a closure for the 4cavity 12, separating it from the c'ounterbore 13,while the conical portion 23 provides a` seal between said counterboreand the atmosphere. At thesame time, the perforations 23 at the topofthe threaded portion 24 provide permanent communication between thechamber 49 and the counterbore 13, whereby the diaphragm motor offthevalve 18 will at all times be maintained at substantially the pressureexisting within said chamber.

Qperatively associated with the valve is a vane or bale member 55movably juxtaposed to the orifice 32, whereby more or less to obstructthe escape of air there'- from, thus to command the operation of thepilot Valve as now to be fully explained.

The sectional view in Figure 1- shows the pilot valve with its severalparts in their normal positions, i. e., the positions they normallyassume when subjected to no uid pressures other than atmospheric,Theplug member 36 will be forced by the influence of the spring 40 into`sealing engagement with the annular bottom portion 25 of the shell 20thereby isolating the chamber 49 from the cavity l2. Underthe influenceof the spring 48 the plate 43 the sleeve 41, and parts integraltherewith will be urged in an upward sense, engaging the plate 33 andforcing the diaphragm 35 to its' topmost position, reducing the space inthe chamber 50 to its minimum internal volume. Upward travel of the plugmember 36 being limited by its engagement with the annular portion 25j,the mating surfaces of said plug member and the sleeve 41 will beseparated, providing free communication between the chamber 49 and theatmosphere.

Upon admission of air pressure from the source 16 tothe cavity 12, airwill be prevented by the plug member 36 from entering the chamber 49 inthe lower part of the shell Ztl, and will build up substantially thesupply pressure in said cavity, with a limited continuous ow through thecapillary bore of the member 34 into the chamber 50. The baffle 55being, as shown inFigure l, an appreciable distance removed from theorice 32, escape of air through said orifice is limited only bydimensions ofvthe opening. The relative dimensions of said orifice andthe capillary 34 being suitably selected with respect to thecharacteristics of the components of the assembly, such pressure as maybuild up in the chamber 50 will be insutiicient to overcome the force ofthe spring 48 whereby to initiate any action of the mechanical parts,which will therefore remain in the respective positions as hereinbeforedescribed; and the control valve 18 will stand with its motor element atatmospheric pressure.

Attention may now be directed to conditions developing when, throughexternal mechanical agency constituting the primary control influence,the baffle member 55 is brought into close juxtaposition to the orifice32 whereby significantly to obstruct the escape of air therethrough,such conditions being fully shown in Figure 2. Obstruction or closure ofthe orifice 32 will cause air pressure to bebuilt up within the chamberSi) until the force upon theidiaphragm over'comes that of the spring 48,causing said diaphragm, the Vplate 33 and the sleeve 41 with attachedparts, tobe moved in a downward sense, bringing the lower surface ofsaid sleeve into sealing engagement with the top of the plug member 36,whereby to cut off communication between the chamber 49 and theatmosphere. Pressure of the sleeve 41 upon the plug member 36 will thencause the latter to be moved in a downward sense in opposition to theforce of the spring 4t), whereby to provide an annular opening aroundthe tapered section 37 of the plug36 and allow free cornmunicationbetween the cavity 12 and the chamber 49. Air `from the supply source 16will now be free to enter said chamber, and, passing throughftheopenings 28 into' escasas 6 the counterbore 13,. to be admitted tothe-motor element ofv the'control valve 18 to actuate the same.

It is to be noted that the surface area-of diaphragm 35 exposed to thepressure developed in chamber 50 is substantially larger than the areaof diaphragm 44 presented toward chamber 49. Because of the relativeareas of diaphragms 35 and 44, when plug member 36 is unseated and thepressure'of the source is transferred to diaphragm 44, the net force isstill downward thereby holding plug member 36 open an amountproportional to the back pressure in chamber 50.

So long as the vane or baffle 55 is retained in the position indicatedin Figure 2, where it more or less obstructs escape of air from theorifice 32, thereby maintaining a substantialpositive pressure in thechamber 50, the movable parts of the pilot valve will remain in therespective positions indicated in Figure 2, and control pressure will bemaintained upon the motor element of the control valve 18. Upon movementof the vane S5 away from its juxtaposition to the orifice 32, asindicated in Figure 1, air will escape through said orifice at anaccelerated rate, so that the pressure within the chamber S) will fallto a value only slightly above atmospheric, whereupon the internal partsof the pilot valve will revert to the respective positions shown inFigure l, the supply of control air will be cut off fromtthe motorelement of the control valve 1S, and the latter,lbeing placed in freecommunication with the atmosphere, will revert to its deenergizedposition.

An important advantage accrues from the type of construction illustratedhere in that clogging of the xed restriction limiting the uid supply tothe valve which has been a common cause of erratic performance andfrequent shut down of pilot valves heretofore known is virtuallyeliminated thereby insuring greatly improved operation. As has beenindicated above, the capillary bore of elongated tubular member 34 formsthe xed restriction referred to and is relatively long in the directionof ow. In fact, tube 34 extends, in the present instance, over the majorportion of the axial length of the valve body itself. As clearly shown,tubular member 34 projects into the inlet chamber formed in air-blockit); consequently there is little or no likelihood of foreign matterwhich may be entrained in the pressure-huid finding its way into andthen clogging the capillary bore. This follows in part from the factthat entrained particles which reach the walls of chamber 12 may not nowbe swept along by the pressure-fluid into the bore due to the portion oftube 34 projecting beyond plug member 36 acting as an obstructionthereto. Furthermore, the extended length of the capillary bore in tube34 functions as a distributed resistance to the low of thepressure-fluid therethrough thereby permitting the use of a borediameter which is large as compared to the diameter of an opening whichis relatively short in the direction of ow to obtain a predeterminedflow-restricting effect and thus further reducing the possibility ofclogging.

In the form of the invention as thus far described, the outside surfaceof the capillary tube member 34 is a sliding fit within the bore of theplug member 36, this being necessary in order to permity relativelongitudinal motion between the two elements whereby the sleeve 41 maybe moved into and out of sealing engagement with the upper surface ofsaid plug member. In this way, there is a continuous leak of air fromthe cavity 12 alongside said tube member to the interior of said sleeve,and thus tothe atmosphere. While the sectional area of the annular spaceabout the tubular member 34 can be made very small in relation to itsaxial length, the clearance essential to positive operation cannot beWhollyv avoided, with the consequence that with the construction shown acertain continuous was'tage of airis unavoidable. In Figure 5 is shownmeans whereby leakage through ..7 the plug 36 may be completelyeliminated. The modification consists in replacement of the plug member36, as described in the previous embodiment of the invention, by a plugmember 56 exteriorly similar to the plug 36 but having its interioropening of considerably greater diameter than the outside of tubularmember 34, and being formed with an enlarged recess 57 at its lowerextremity. In assembly, the tubular member 34 is surrounded by atight-litting annular diaphragm 58 of rubber or similar yielding andnon-permeable material, sealed to the lower extremity of said tubularmember to form an airtight joint, and having a convolute portion adaptedto lie in the recess 57 and a flat portion adapted to rest upon thebottom part of said plug. The diaphragm 58 is secured to the bottom ofthe plug 56 by means of a clamping ring 59 provided with claws or lugspressed into suitable openings formed in the lower cylindrical portionof said plug. The exible diaphragm 58 thus provides a positive sealbetween the cavity 12 containing air at supply pressure and the chamber51 which communicates freely with the atmosphere. Such axial force asmay be exerted on the diaphragm 58 due to the excess of supply overatmospheric pressure will tend to move the tubular member 34 andattached parts toward the upper part of the shell; and as relativemotion between said tubular member and the plug membei' 56 is permittedby the convoluted portion of the diaphragm 58, such displacement willnot adversely affect the performance of the unit as a whole under any ofits operating conditions.

The terms and expressions which I have employed are used as terms ofdescription and not of limitation, and I have no intention, in the useot' such terms and expressions, of excluding any equivalents of thefeatures shown and described or portions thereof, but recognize thatvarious modiiications are possible within the scope of the inventionclaimed.

What is claimed is:

l. A pilot valve adapted to control the flow of a fluid from a pressuresource to a motor element in response to variations in the flow of arelatively small volume of fluid initiated by independent control means,comprising a substantially hollow body having an inlet adapted to becoupled to said source and an outlet adapted to be coupled to said motorelement, movable means forming with spaced portions of the interior ofsaid body a first variable-volume chamber normally having apredetermined volume and a second chamber, said movable means includinga plate-like member having a predetermined surface area extendingtransversely to an axis of said body, said body having an orilice formedtherein affording communication between said first chamber and theatmosphere, an elongated tubular member engirdled by said movable meansaxially extending in said body and having an open ended capillary boreformed therein throughout its length of substantially uniform diameterand communicating through said movable means with said first chamber,said bore communicating through said inlet with said source when saidbody is coupled thereto so that a small volume of uid normally passesfrom said source through said bore into said rst chamber to escapethrough said orifice, said second chamber being in communication withsaid inlet and outlet and normally in communication with the atmospherethrough an opening in said body, said inlet, orifice and tubular memberbeing axially aligned one with the other and coaxial with said hollowbody, plug means actuated by said movable means and normally sealingsaid inlet, said plug means having a surface area transversely to saidaxis'which is substantially less than said predetermincdesurface area,said .bore communicating through said plug means with said source, andsaid movable means being shiftable on increase in the volume of said rstchamber to seal oi said second chamber from the atmosphere and actuatesaid plug means to open said inlet.

2. A pilot valve adapted to control the ow of va fluid from a pressuresource to a motor element in response to variations in the ow of arelatively small volume of iuid initiated by independent control means,comprising a substantially hollow body having an inlet adapted to becoupled to said source and an outlet adapted to be coupled to said motorelement, movable means forming with spaced portions of the interior ofsaid body a iirst variable-volume chamber normally having apredetermined volume and a second chamber, said movable means includinga plate-like member having a predetermined surface area extendingtransversely to an axis of said body, said body having an orilice formedtherein affording communication between said first chamber and theatmosphere, an elongated tubular member engirdled by said movable meansaxially extending in said body and having an open ended capillary boreformed therein, said tubular member extending through said movable meanswith said bore communicating with said first chamber, said tubularmember extending through said inlet and beyond said body with said borein communication with said source when said body is coupled thereto sothat a small volume of fluid normally passes from said source throughsaid bore into said chamber to escape through said orifice, said secondchamber being in communication with said inlet and outlet and normallyin communication with the atmosphere through an opening in said body, aplug member surrounding a portion of said tubular member and axiallydisplaceable relative thereto from sealing engagement with said inlet toa position opening said inlet, said plug member having a surface areatransversely to said axis which is substantially less than saidpredetermined surface area, said tubular member extending through saidplug member, and said movable means being shiftable on increase in thevolume of said first chamber to seal olf said second chamber from theatmosphere and to move said plug member to its open position.

3. A pilot valve adapted to control the ow of a fluid from a pressuresource to a motor element in response to variations in the flow of arelatively small volume of fluid initiated by independent control means,comprising a substantially hollow body having an inlet adapted to becoupled to said source and an outlet adapted to be coupled to said motorelement, movable means forming with spaced portions of the interior ofsaid body a first variable-volume chamber normally having apredetermined volume and a second chamber, said movable means includinga plate-like member having a predetermined surface area extendingtransversely to an axis of said body, said body having an orifice formedtherein affording communication between said first chamber and theatmosphere, an elongated tubular member engirdled by said movable meansaxially extending in said body and having an open ended capillary boreformed therein, said tubular member extending through said movable meanswith said bore communicating with said first chamber, said tubularmember extending through said inlet and beyond said body with said borein communication with said source when said body is coupled thereto sothat a small volume of fluid normally passes from said source throughsaid bore into said chamber to escape through said oriiice, said secondchamber being in communication with said inlet and outlet and normallyin communication with the atmosphere through an opening in said body, aplug member surrounding a portion of said tubular member and axiallydisplaceable relative thereto from sealing engagement with said inlet toa position opening said inlet, said plug member having a surface areatransversely to said axis which is substantially less than saidpredetermined surface area, said tubular member extending through said.maca-aes `9 t plug member, resilient means urging-said .movable means'in a direction to maintain the predetermined volume of said firstchamber and said plug member into sealing;engagement with said opening,and said movable means being shiftable on increase in the volume of saidfirst chamber to seal off said second chamber from the atmosphere and tomove said plug member to its open position. y

4. A pressure responsive valve for controlling the passage therethroughof a fluid from a pressure source, comprising a substantially hollowbody adapted to be coupled to said source and having an inlet and anoutlet for said fiuid as Well as an orifice formed therein, firstmovable means forming with a portion of the interior of said body afirst variable-volume chamber communicating with said orifice, saidmovable means including a plate-like member having a predeterminedsurface area extending transversely to an axis of said body, anelongated tubular member axially extending insaid body and having anopen ended capillary bore formed therein throughout its length ofsubstantially uniform diameter and communicating through said firstmovable means with said first chamber, said bore communicating also withsaid source when said body is coupled thereto, said first chambercommunicating with said orifice and with said capillary bore, secondmovable means `movable independently of and actuated by saidfirstmovable means and forming with other portions of said body a secondchamber inV communication with said inlet and outlet openings, plugmeansactuated by said second movable means and movable into and out ofsealing engagement with said body for closing and opening said inlet,said second movable means and said plug means having a surface areatransversely to said axis which is substantially less than saidpredetermined surface area, said tubular member extending throughv saidsecond movable means and said plugy means, said second movable means inone position providing communication between said second chamber and theatmosphere and in another position sealing ofi said second chamber fromthe atmosphereA and actuating said plugv means to open said inlet, andsaid inlet, orifice, tubular member and first and second movable meansbeing axially aligned one with the other and coaxial with said hollowbody, whereby uid may continually reach said first chamber from saidsource through said capillary bore and when the pressure of the fluid insaid first chamber is substantially at atmospheric pressure said secondchamber is maintained in communication with the atmosphere and sealed offrom said source. d

5. A pilot valve adapted to control the ow of a fluid from a pressuresource to a motor element in response to variations in the fiow of a`relatively Vsmall volume of fiuid initiated by independent controlmeans,'comprising a substantially hollow body havingan inletl adapted tobe coupled tosaid source and an'outlet adapted'toI be coupled to saidmotor element, first movable diaphragm ingwithotherportions of 4saidbody ya second chamlef .in communication with said inlet and saidoutlet, 'said second diaphragm means including an annular `member havingan inner space normally communicating with the atmosphere and with saidsecond chamber, plug means actuated by and normally spaced from saidsecond vdiaphragm means and normally sealing said inlet, said seconddiaphragm means and said plug meanshaving a` surface area transverse tosaid axis which is substantially less than said predetermined surfacearea, said elongated tubular member extending through said annularmember and said plug means, said second diaphragm means when actuated bysaid first movable means being shiftable into engagement with said plugmeans to seal said second chamber from the atmosphere and to shift saidplug means out of its normal position to open said inlet, Vsaid inlet,orifice tubular rmember andfirstand second movable diaphragm means beingaxially aligned on'evwith the other and coaxial with said lhollow body,whereby a reduction in the escape ofvtiuid through said orifice as maybe initiated by said independent control means causes an increase in thevolume of said first chamber and a consequent sealing of said secondchamber from the atmosphere and opening 'of said inlet.

6. A pilot valve adapted to control the flow of a uid from a pressuresource to a motor, element in response to variations in the flow of arelatively small volume of fluid initiated by independent control means,comprising a substantially hollow'body having an inlet adapted to becoupled to said source and an outlet adapted to be coupled to said motorelement, first movable diaphragm means forming with a portion of theinterior of said body a first Avariable-volume chamber normally havingIa predetermined volume, said first movable diaphragm means forming witha portion of the interior of lsaid` body a first variable-volume chambernormally Ahaving a predetermined volume, said first movable diaphragmmeans having a predetermined; surface area extending transversely to anaxis oflsaid body, said body havingan orifice formed therein affordingcommunication between said first chamber andthe atmosphere,'an elongatedtubular member axially extending in said body and having an open endedcapillary bore lformed therein throughout its length of substantiallyuniform diameter and communicating through said first diaphragm meanswith saidfirst chamber and through said body with said source when saidbodyis coupled thereto so that a jsmall volume of fiuid normally passesfrom said source through said bore into said first chamber to escapethrough said orifice, secondI movable diaphragmmeans movableindependently of and actuated by said first diaphragm means andformmeans having a predetermined surface area extending transversely toan axis of' said body, said body having an orifice formed thereinaffording communication between said first chamber and the atmosphere,an elongated tubular member axially extending in said body and having anopen ended capillary bore formed therein, said tubular member beingsealed through said first diaphragm means with said bore communicatingwith said first chamber, said tubular member extending through saidinlet and beyond said body with said'bore in communication with saidsource when said body is coupled thereto so that a small volume of fluidnormally passes from said source through said bore into said chamber t'oescape through said orifice, second movable diaphragm means actuated bysaid first diaphragm means and forming with other portions of said bodya second chamberV surrounding said tubularmember and in communicationwith said inlet andsaid outlet, a plug member surrounding a'portion ofsaid tubular member and axially displaceable relative thereto fromsealing engagement with said inlet to a position opening said inlet,said seconddiaphragm means and said plug member having a surface areatransverse to said axis which is substantially less than saidpredetermined surface area, said second diaphragm meansv in one positionproviding communication between said secondchamber and'the atmosphereand in another position sealing off said second chamber fromtheatmosphere and displacing said plug member to open said inlet therebyplacing said second chamber in communication with said source, whereby areduction in the escape of fluid throughsaid orifice as may be initiatedby said independent control means causes an increase in the volume ofsaid first chamber and a consequent sealing `of said second chamberfromfthe atmosphere and opening of said inlet.

7. A pilot valve adapted to'control the fiow of a fiuid from a pressuresource to a motor element in response to variations in the fiow of arelatively small volume of fluid-initiated by independent control means,comprising a substantially hollow body having an inlet adapted to becoupled `to said source and an outlet adapted to be coupled to saidmotor element, 'first movable diaphragm means forming with a portion ofthe 'interior of said body a first variable-volume chamber normallyhaving a predetermined volume', said first movable diaphragm meanshaving a predetermined surface area extending transversely to an axis ofsaid body, said body having an orifice formed therein affordingcommunication between said first chamber and the atmosphere, anelongated tubular member axially extending in said body and having anopen ended capillary bore formed therein, said tubular member beingsealed through said first diaphragm means with said bore communicatingwith said first chamber, said tubular member extending through saidinlet and beyond said body with said bore in communication with saidsource when said body is coupled thereto so that a small volume of fluidnormally passes from said source through said bore into said chamber toescape through said orifice, second movable diaphragm means actuatedbysaid first diaphragm means and forming with other portions of saidbody a second chamber surrounding said tubular member and incommunication with said inlet and said o utlet, a plug membersurrounding a portionvof said tubular member and axially displaceablerelative thereto from sealing engagement with said inlet to a positionopening said inlet, said second diaphragm means and said plug memberhaving a surface area transverse to said axis which is substantiallyless than said predetermined surface area, said second diaphragm meansin one position providing communication between said second chamber andthe atmosphere and in another position sealing off said second chamberfrom the atmosphere and displacing said plug member to open said inletthereby placing said second chamber in communication with said source,and resilient means urging said second diaphragm means toward said oneposition thereof and urging said plug member into sealing engagementwith said inlet, whereby a reduction in the escape of fluid through saidorifice as may be initiated by said independent control means causes anincreasein the volume of said rst chamber and a consequent sealing ofsaid second chamber from the atmosphere and opening of said inlet.

8. In'a pilot valve for controlling the flow of a fluid from a pressuresource to a conduit in response to variations in the flow of arelatively small volume of fluid from said source initiated byindependent control means, an enclosing member, movable means formingwith interior walls of said enclosing member a variable-volume chambernormally communicating with the atmosphere through an orifice centrallyformed in said enclosing member in one side thereof, said enclosingmember further'having an inlet adapted to be coupled to said sourcecentrally formed in the opposite side thereof registering with saidorifice and an outlet adapted to be coupled to said conduit, saidmovable means includinga closure for said inlet, an elongated tubularmember axiallyalined with said orifice and said inlet having anelongated axial capillarybore formed therethrough extending through saidmovable means and on one side thereof communicating with said chamberand on the other side thereof projecting through and beyond saidclosure'to receive fluid from said source when said enclosing member iscoupled thereto and when said closure limits the flow of fluid throughsaid inlet, said *bore forming the sole communication between Asaidsource and said chamber, Vwhereby a volume of fluid restricted by saidbore may normally flow from said source to said variable-volume chamberand through said orifice. i

9. In a pilot valve for controlling the flow of a relatively greatvolume of fluid from a pressure source to a motor element by varying theescape of a relatively small volume of fluid from said source bychangesV in the position of a juxtaposed movable bale, the combinationof anrenclosing member having sealed therein a larger and a' smallerflexible diaphragm, said diaphragms being rela- A4 .Atigvgly displacedand independently movable along a' commonv axis and separatelycooperating with internal walls of said enclosing member to formrespectively a first and a second variable-volume chamber, the firstchamber, formed by said larger diaphragm, communicating with theatmosphere through an orifice adapted to be more or less obstructed bysaid movable baille, and the second chamber, formed by said smallerdiaphragm, communicating with said source through an inlet opening in awall of said enclosing member, a plug member adapted for limitedmovement along said axis more or less to obstruct said inlet opening, aspring element normally maintaining said plug member in a position toclose said inlet opening, a tubular member attached to said largerdiaphragm, passing axially and freely through the plug member and havinga capillary bore to provide restricted communication betwen said sourceand said first chamber, an annular member axially movable with saidsmaller diaphragm, encircling said tubular member between said largerdiaphragm and said plug member and having its inner space incommunication with the atmosphere, said annular member being adapted toseat upon said plug member to seal said second chamber fromcommunication with said inner space and upon further displacement toforce said plug member away from its position of sealing said opening,spring means urging said annular member away from engagement with saidplug member to permit free communication between said second chamber andthe atmosphere and to urge said larger diaphragm in a sense to minimizethe volume of said first chamber, and means for permitting fluidcommunication between said second chamber and said motor element.

VlO. A pilot valve for cooperation with an air-block having an innercavity connected to a fluid-pressure supply and an outer cavity coaxialtherewith and connected to a fluid-operable motor element and having aninternally threaded section between said cavities, and for the purposeof controlling the ow of an expansible fluid from said inner to saidouter cavity and alternatively from said outer cavity to the atmosphere,said pilot valve comprising an enclosing shell having a base member anda cover member, said base member including an externally threadedlportion adapted to cooperate with the internally threaded sectionbetween said cavities in securing said shell in said air-block and inproviding a seal between said cavities, an expanded conical portionadapted to cooperate With the edge of said outer cavity in sealing thesame from communication with the atmosphere and perforated to providecommunication between the interior of said base portion and said outercavity, and a further expanded portion having a flat section and adaptedfor sealing engagement with said cover member and provided withperforations in said flat section whereby the interior of said furtherexpanded portion is in communication with the atmosphere, a movable plugmember having an axial bore therethrough and externally adapted tocooperate with said base portion to seal the interior thereof fromcommunication with said inner cavity, spring means normally tending tomaintain said plug member in sealing realtionship with said baseportion, a first flexible diaphragm sealed between said further expandedportion of said base member and said cover member to form a firstvariable-volume enclosed chamber within the latter, said cover memberhaving an orifice to provide controllable fluid therethrough from saidfirst chamber to the atmosphere, a tubular member attached to saiddiaphragm, projecting into said inner cavity, and passing freely throughthe vaxial bore of said plug member whereby to provide restrictedcommunication between said inner cavity and said first chamber, a secondflexible diaphragm adapted to lie within said further expanded portion,a

ring member adapted to engage the edge of said second` diaphragm andprovided with axially extending lug portions ,passing through saidperforations and bent over whereby said ring member secures saidseconddiaphragm against the flat section of said further expandedportion in sealing relation to form a second variable-volume chamberwithin the interior of said base portion and in communication with saidouter cavity, an annular member axially movable with said seconddiaphragm, encircling said tubular member between said first diaphragmand said plug member and having its inner space in communication withthe atmosphere and adapted to seat upon said plug member to seal saidsecond chamber from communication with said inner space and upon furtherdisplacement to force said plug away from its position of sealingcooperation with said base portion, spring means urging said annularmember away from seating relation with said plug member to permit freecommunication between said second chamber and the atmosphere and to urgesaid first diaphragm in a sense to minimize the volume of said firstchamber.

11, A pilot valve as set forth in claim 2 comprising means movablysealing said tubular member and said plug member one to the other.

12. A pilot valve as set forth in claim 2 comprising a flexiblediaphragm extending between and connected to said tubular member andplug member providing a seal therebetween while permitting displacementof said tubular member relative to said plug member.

13. In a pilot valve as set forth in claim 8, exible means extendingbetween said tubular member and said closure providing a sealtherebetween while permitting displacement of said tubular memberrelative to said closure.

References Cited in the file of this patent UNITED STATES PATENTS560,230 Powers May 19, 1896 1,666,270 Soderberg Apr. 17, 1928 1,834,773Fellman et al Dec. 1, 1931 2,187,465 Simonick Ian. 16, 1940 2,261,827Brown NOV. 4, 1941 2,566,708 Trevaskis Sept. 4, 1951 2,629,365 KennedyFeb. 24, 1953 2,635,618 Moore Apr. 21, 1953 2,751,918 Higgins June 26,1956 FOREIGN PATENTS 233,110 Germany Mar. 29, 1911 560,201 Great BritainMar. 24, 1944

